Speaking at the OPIS National Supply Summit in San Antonio, Citgo's senior vice president of supply & distribution said roughly 40 percent of the U.S. refining capacity has not even initiated the extensive design engineering that will be required to bring the annual average of sulfur content down from 120 parts per million (ppm) to an average 30 ppm.

"Most of those refineries that have not yet committed to engineering are probably planning to take advantage of credits and allotments to delay their investment, but some will forego the necessary investment altogether and will eventually shut down," he said.

Thompson also discussed new vehicle technologies and the fuels that will power them. "The best fuel for the future should be determined by whatever combination of fuel and engine provides the best efficiency at the least cost," he said. "Today, that is the gasoline-powered internal combustion engine, and I am convinced that gasoline will continue to be the fuel of choice for at least the next 25 years and probably beyond."